Mobile phones and many other small and medium size OLED screens use R, G, B sub-pixel display mode (FIG. 1). In order to improve the production yield, some functional layers are often designed as public layers, so that FMM (fine metal mask) can be used less. Hole transporting layer often uses a public layer, and general public hole transporting layer may use commercially available materials. The commercially available hole transporting layer materials have a molecular structure of, e.g.
However, such material has a higher longitudinal mobility rate, and the lateral mobility rate thereof is not very high. There will be no occurrence of crosstalk between pixels.
CN103108859 discloses
wherein the material has a good solubility, and a higher mobility rate.
There are several problems in the current technologies of hole transporting materials. First, the material solubility is not good, which leads to a poor cleaning effect of masks for evaporation during mass production. Second, the material mobility rate is too low, which will lead to an excessive overall voltage of devices. Third, the mobility rate of the material, especially the lateral mobility rate of the material, is too high, leading to crosstalk of adjacent pixels.
The mobility rate of the commercially available material in EP-721935 falls within the acceptable range, and no crosstalk will occur. However, the solubility thereof is not very good. The solubility of the commercially available material in CN103108859 is acceptable, but too high mobility rate leads to lateral leakage current to form crosstalk.
There is a need in the field for the development of OLED devices which have small crosstalks between pixels and are suitable for mask cleaning process.